The current single input is provided through social networks and does not significantly degrade authorization (or registration). Often, the user still needs to enter additional data.
If it concerns exchanges or sites that require you to verify the identity with the help of documents, then they have to develop their own authorization tools.
My project also offers to register on the service, enter the necessary documents. Our specialists will check everything. And, if necessary, you can log in any other ways.
Advantages:

• faster (you do not need to create an account every time, you do not have to wait for the exchange or which service to approve your identity using documents)
• safer (you do not need to send out all your documents to authorize your identity)